Take butter, yogurt, vegetable oil, egg yolk, and vinegar in a large mixing bowl and whisk it well. Add baking soda, salt. Add flour slowly (to make very soft dough ) and start to knead.Stop adding flour when you reach soft consistency.
Preheat the oven 350F. Place a parchment paper on a baking sheet.Take small parts ( about the size of a half walnut ) from the dough and give them the shape of ring (about 2 inch diameter).Take the egg white and sesame seeds in a separate bowls.Dip the rings first into egg white and then dip them into sesame seeds.Place the rings on the baking sheet.Bake them until the rings are just golden brown.

Hi Maja, Tuz means salt in Turkish as Turkish kitchen says in her reply. There's a salt lake in your city in Bosnia, no? And there were marshes near the city of Tuzla near Istanbul where salt used to be collected but has now become too polluted. So there's the conection. It's nice to see people from all over the Balkans and Turkey connect. Niko